1. Field of the Invention
The present invention relates to a method for improving contact hole patterning, and more particularly, to a method of fabricating a contact hole with a post treatment process.
2. Description of the Related Art
Since a liquid crystal display (LCD) has the advantages of portability, low power consumption, and low radiation, the LCD has been widely used in various portable information products, such as notebooks, personal digital assistants (PDA), etc. The LCD is gradually replacing the cathode ray tube (CRT) monitors of the conventional desktop computers. Among all kinds of LCDs, the thin film transistor liquid crystal display (TFT-LCD), which can drive pixels disposed on the liquid crystal display panel with an active matrix driving method, is therefore a major focus.
In the fabricating process of the thin film transistor, an inter-layer dielectric (ILD) layer is disposed between the transistor and the metal layer thereon for isolating and protecting the electrical elements on the LCD panel. A plurality of contact holes are formed in the ILD layer so that the metal layer can be filled into the contact holes to electrically connect with the transistor or other electrical elements. Therefore, data signals can be transmitted to a source and a drain of the transistor through the metal layer inside the contact hole for controlling the operation of pixels in the LCD panel.
Please refer to FIG. 1 to FIG. 3, which are schematic diagrams of a method of fabricating a contact hole in an LCD panel 10 according to prior art. As shown in FIG. 1, the LCD panel 10 comprises a substrate 12, a conductive layer 14 disposed on the surface of the substrate 12, and a dielectric layer positioned on the conductive layer 14. The LCD panel 10 can further comprises other electrical elements, such as a plurality of gate structures of driving transistors (not shown). The conductive layer 14 serves as a source or a drain of the driving transistor. The dielectric layer 16 is used for isolating the driving transistor from other electric elements and providing a plane surface for the following process. In the conventional method of fabricating a contact hole, a lithography process is first performed,to form a photoresist layer 18 on the dielectric layer 16. The photoresist layer 18 comprises an opening 20 extending through to the surface of the dielectric layer 16 for defining the pattern and the position of the contact hole.
As shown in FIG. 2, an etching process, such as a dry etching process or a wet etching process, is followed by using the photoresist layer 18 as a mask layer to remove parts of the dielectric layer 16 along the opening 20 and form a contact hole 22 extending to the surface of the conductive layer 14. As shown in FIG. 3, after the photoresist layer 18 is stripped, a conductive material, such as a doped polysilicon or a metal layer, is filled into the contact hole 22 to form a conductive trace or a contact plug for electric connection of the driving transistor or other electric elements on the LCD panel 10.
Since each driving transistor on the LCD panel 10 corresponds to a pixel, the electrical performance of each driving transistor determines the uniformity of the LCD panel 10 display. For improving the display performance of the LCD panel 10, a base solution with amine is used as a photoresist stripper (PR stripper) to remove the photoresist layer 18 on the LCD panel 10 uniformly so as to avoid the pollution caused by the residual photoresist layer 18. However, the conductive layer 14 in the bottom of the contact hole 22 is exposed to the amine-contained stripper when the photoresist layer is stripped. As a result, damage on the surface of the conductive layer 14 occurs very frequently. These will all result in point defects, which deteriorate the stability of data transmission and affect the reliability of products.
It is therefore a primary objective of the claimed invention to provide a method of forming a contact hole on an LCD panel which comprises a post treatment process to form a protective layer on the conductive layer to solve the problem mentioned above.
In a preferred embodiment of the claimed invention, an LCD panel comprises a substrate, a conductive layer disposed on the surface of the substrate, and a dielectric layer positioned on the substrate. First, a photoresist layer is formed on the dielectric layer. The photoresist layer comprises an opening extending through to the surface of the dielectric layer. Then, an etching process is performed to remove parts of the dielectric layer along the opening to form a contact hole extending to the surface of the conductive layer. A post treatment process is followed to form a protective layer on the conductive layer. After the photoresist layer is stripped, the protective layer is removed and a conductive trace electrically connected to the conductive layer through the contact hole is formed on the dielectric layer.
It is an advantage of the claimed invention that a post treatment process is performed to form a protective layer on the conductive layer to prevent the conductive layer from being exposed to amine-contained stripper. Therefore, the method of the claimed invention prevents damage on the conductive layer sufficiently and thereby improves the reliability of the products in advance.
These and other objectives of the claimed invention will not doubt become obvious to those of ordinary skill in the art after reading the following detailed description of the preferred embodiment, which is illustrated in the various figures and drawings.